Pain for the banks

I was browsing BoIs mortgage terms and conditions (out of interest, you know) and came across this:

Does this mean that assets securitised are at a 15% discount? So the banks won’t feel pain until property falls 15%?

Edit: I found this:
ifsra.ie/data/in_bci_files/R … 2041.1.pdf
but it doesn’t clear a lot up for me except there is one interesting bit on the valuation of Irish residential-backed paper:

Does this explain the mythical content of the PTSB/ESRI index? At the very least it makes it suspect as it directly affects what banks can value their securitisations at for repo purposes? (Where they sell the security to themselves).